Purging Your Filament Maker

The essential article to help you learn the basics of purging your machine. What materials to use, what to prepare, what are the machine settings, and what are the different types of purging.

Table of contents

Definition

When to purge?

Machine Settings

Purging Materials

Types

Preparations

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If you try and "empty" the machine, there will always be leftover residue, which will burn, degrade or even damage the Filament Maker. which brings us to...

What is purging?

If you are unfamiliar with the process and its importance, please start by reading our dedicated article: What is Purging?

When to purge the Filament Maker?

Every single time after use!

Purging material can be left in the machine. Polymers cannot be left in the machine. Even if you plan on processing the same material several times in a row. The one exception is when processing virgin PLA (from 3devo). In our own experience there are only three materials which do not need purging:

1. virgin PLA (3devo)
2. HDPE
3. DevoClean MidTemp

Please note, these materials should be raw materials without any additives. 

What are the machine settings?

There are no purging presets.

Temperature

You should always use the same temperatures you were using to process the material you are about to purge (because it, too, must melt). Those temperatures must also be included in the thermal range of the purging material. See Purging Materials below.

Screw speed

5 - 15 RPM

Naturally, it depends on what material you are about to purge out of the machine.

      5 RPM is the base line. Some basic materials like PLA have "Machine Presets" at 5 RPM.

      10 RPM can help speed things up, if the purge has a good flow.

      15 RPM is used for regular high speed purging, but observe the material flow carefully, and
      avoid dangerous pile ups.

If you encounter a stubborn material that is difficult to clean, you can also try Disco Purging. This method creates turbulence in the flow of the purge by randomly changing the speed of the scree every minute.

Find out more about Disco Purge.

Duration

It depends.

You must keep purging until you get a pure output of purging material, free of any other material or impurity. Under normal circumstances, this usually takes about 15-25 minutes, but it can take a lot more time:

• when two purging materials are involved (DevoClean HighTemp and DevoClean MidTemp)
• if the material is very persistent (contains colorants and/or additives)
• if the screw is partially stuck, the flow is weak, and you are trying to get a good flow back

Amount of purging material

It depends.

150-200g is the minimal amount required, but some processes involving multiple transitions or persistent substances can consume more than 400g. The objective is to ensure that none of the previous material has been left inside the barrel. You will need to keep feeding the hopper until this condition is met.

What purging material can I use?

A purging material is defined by:

• Its capacity to remove impurities from the barrel. Abrasive additives can help.
• Its thermal range. This window of temperatures must match the process temperature of the material you wish to purge out.

Purging Materials

A variety of purging materials exists on the market. At 3devo we use the three following options as we know them very well and their combined thermal range covers almost all existing plastics.

Name	Purging Capacity	Thermal Range (°C)	Can I leave it safely inside the barrel after shutdown?	When to use it?
HDPE	medium	180-280	Yes	To purge virgin plastics or remove DevoClean MidTemp.
DevoClean MidTemp	high	200-300	Yes	To purge any material in the thermal range, including composites. Use it if anything goes wrong during the extrusion (impurity coming out, flow stopping etc).
DevoClean HighTemp	very high	290-400	No	After DevoClean MidTemp at 295°C to reach higher temperatures. To purge high temperature materials (PEEK,…) Note: It must be purged with DevoClean MidTemp at 300°C after use.

Types

Different types of filament materials call for different ways of purging. The way of purging the extruder is based on the melt temperature, viscosity, and the use of additives such as colorants, fibres and fillers. Also the state of the machine plays a part, for example if the extruder is filled with burnt material, heavier purging might be necessary.

The ways of purging can be divided into the following:

1. Standard Purge
   This is carried out with DevoClean MidTemp (middle temperature) and can generally be applied to all situations if the polymer material has a range of 180-320°C.
2. Heavy Purge
   A heavy purge is done with DevoClean HighTemp (high temperature) at a range of 280-420°C.

These levels have their own step by step guides. Please refer to them when purging your Filament Maker. 

Preparations

Before purging your extruder, there are a few preparation steps that should be taken for safety.

1. Gathering
   The first step is gathering all the necessary tools, materials and information for the purging process. These are:
   • at least 350 grams of purging material, however this will depend on:
     • which level of purging you are using
     • the type of material that needs to be purged out of the machine
     • and the machine’s state
   • a piece of paper or cardboard
   • tape
   • multitool (or a side cutter and pincers)
2. Ventilation
   Make sure that the area is properly ventilated. A fume hood is also highly recommended to guarantee your safety, especially with Heavy purges. Wearing a gas mask is also a good option.
3. Sensors
   Turn off the hopper sensor in the "Settings" menu, so the hopper can be run completely empty before putting in the purging material. Do this by setting "off" under "Hopper empty check".
4. Fans
   Turn off the filament fans by setting the "Filament fan speed" to 0% in the "Settings" menu, and point them as in the picture below.
5. Cardboard
   Cover the filament sensor with the piece of paper or cardboard and hold it in place with a piece of tape.

Setup of the filament maker for a purging run

 

Once again, the type of purging you will carry out depends on a lot of factors, including materials, temperatures, and additives. Please follow the guides for each type of purge below: 

Standard Purge